Families with babies and young children are left to fend for themselves because there are no creche facilities.
Susan Stranks, director of the voluntary organisation which campaigns for more National Lottery profits to be invested in children, claimed the deliberate exclusion of the needs of the youngest visitors would put families off.
"Such a gap in basic family provision is symptomatic of much policy-making these days," she said. "Around boardroom tables sit high-powered 40 and 50-somethings who haven't spent much time pushing buggies.
"Many households include members under seven years old. The majority of parents have no place to leave their infants and toddlers, even if they want to, to enable them to enjoy the six, long hours recommended to gain full appreciation of the Dome.
"Young children need a anctuary away from too much noise and confusion."
Attractions aimed specifically at very young children were also thin on the ground at the Dome, according to the campaigners.
Mrs Stranks said: "If new chief executive Pierre-Yves Gerbeau wants more families to visit and enjoy the Dome, his priority should be to install a safe and stimulating area where infants, toddler and pre-school kids can indulge in fun and discovery, under the care and supervision of qualified nursery staff."
A spokesman for the Dome said a creche would not be appropriate because the attraction was designed as a family day out.
"Families are supposed to enjoy the Dome together. The strict legislation covering childcare staff and cost would also make it prohibitive."
The spokesman claimed that a number of attractions such as the Time Keepers' Zone, which contained a staffed play area, and the Home Planet Zone were suitable for younger children.